Glutamate is the most abundant excitatory neurotransmitter in the brain, and glutamatergic synapses play a critical role in learning, memory, and developmental plasticity of the central nervous system. It is critical to understand how glutamatergic synapses are formed and regulated in the CNS in order to develop novel applications for the diagnosis, treatment, and prevention of neurological disorders. Several fundamental questions remain unanswered. How are glutamate receptors and signaling molecules localized specifically to glutamatergic synapses? How are these neuron-neuron synapses made and modified during development? C. elegans has been an excellent model system for studying glutamate signaling in vivo with an emphasis on how glutamatergic synapses are formed and modified during development. The AMPA-type glutamate receptor (GluR) subunit GLR-1 is required for glutamatergic signaling and is localized to synaptic clusters between C. elegans neurons. We are interested in determining how GLR-1 localization (and the localization of glutamate receptors in general) is conducted and regulated. By forward genetic screening, we have identified several genes that when mutated result in defects in GLR-1 localization. This proposal aims to characterize three genes identified through those screens. First, we will conduct a structure/function analysis of UNC-43, a CaMKll homolog required for GLR-1 localization. We will introduce mutations into specific domains of UNC-43 to test the ability of the mutant proteins to localize to synapses and to rescue unc-43 mutants for GLR-1 localization defects. Second, we will characterize two newly-identified genes, glo-2 and glo-11, that are required for GLR-1 localization. We will clone glo-2 and glo-11, determine in which cells GLO-2 and GLO-11 proteins are expressed, and determine where GLO-2 and GLO-11 proteins are localized within the cell. Third, we will complete the screen that identified glo-2 and glo-11 to saturation. Candidate genes will be subjected to rigorous criteria to determine which genes merit further study. Interestingly, the function of UNC-43/CaMKII is conserved across phylogeny. Thus, we expect our future experiments with this system to reveal universal principles about the formation and function of the central nervous system, and perhaps suggest new strategies for the treatment of human neurological disorders.